def next_coord( w, h ):
    """
    get the next x,y coordinates around your box
    w,h are the width and height of your box

    note, the strange ranges are to prevent getting the corners twice
    this loop configuration goes around clockwise from top left

    for x,y in next_coord(3,3):
        print "(%d,%d)" % (x,y),
    >>> (0,0) (1,0) (2,0) (2,1) (2,2) (1,2) (0,2) (0,1)
    """
    for x in range(0,w-1):        # top
        yield x,0
    for y in range(0,h-1):        # right
        yield w-1,y
    for x in range(w-1,0,-1):     # bottom
        yield x,h-1
    for y in range(h-1,0,-1):     # left
        yield 0,y